/
scanner.js
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/
scanner.js
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/*!
* node-hbase-client - lib/scanner.js
* Copyright(c) 2013 fengmk2 <fengmk2@gmail.com>
* MIT Licensed
*/
"use strict";
/**
* Module dependencies.
*/
var EventEmitter = require('events').EventEmitter;
var util = require('util');
var async = require('async');
var Linklist = require('algorithmjs').ds.Linklist;
var Result = require('./result');
var Scan = require('./scan');
function Scanner(server, id, scan, region, client, tableName) {
EventEmitter.call(this);
this.server = server;
this.id = id;
this.scan = scan;
this.closed = false;
this.cache = new Linklist();
this.region = region;
this.client = client;
this.tableName = tableName;
}
util.inherits(Scanner, EventEmitter);
Scanner.prototype._openNextScanner = function(callback) {
// no more region
if (!this.region.endKey || !this.region.endKey.length) {
return callback(null, false);
}
// next region is bigger than scan.stopRow
if (this.scan.stopRow.length && this.region.endKey.compare(this.scan.stopRow) === 1) {
return callback(null, false);
}
var old = this.scan;
var scan = new Scan(this.region.endKey, old.stopRow);
scan.maxVersions = old.maxVersions;
scan.batch = old.batch;
scan.caching = old.caching;
scan.maxResultSize = old.maxResultSize;
scan.cacheBlocks = old.cacheBlocks;
scan.filter = old.filter;
scan.tr = old.tr;
scan.familyMap = old.familyMap;
var self = this;
this.client.getScanner(this.tableName, scan, function(err, scanner) {
if (err) return callback(err);
self.server = scanner.server;
self.id = scanner.id;
self.scan = scan;
self.region = scanner.region;
return callback(null, true);
});
};
Scanner.prototype._next = function(callback) {
if (!this.cache.length && this.closed) {
return callback(null, null);
}
if (this.cache.length) {
return callback(null, this.cache.popFront());
}
// cache from server
var self = this;
var caching = this.scan.caching < 1 ? 1 : this.scan.caching;
var countdown = caching;
var nextFinished = false;
var values = [];
async.whilst(function() {
return countdown > 0 && !nextFinished;
}, function(callback) {
self.server.nextResult(self.id, caching, function(err, rows) {
if (err) {
return callback(err);
}
if (rows.length) {
countdown -= rows.length;
values = Array.prototype.concat.apply(values, rows);
}
if (rows.length < caching && countdown > 0) {
return self._openNextScanner(function(err, opened) {
if (err) return callback(err);
nextFinished = !opened;
callback();
});
} else {
return callback();
}
});
}, function(err) {
if (err) return callback(err);
if (!values.length) return callback();
values.forEach(function(v) {
self.cache.pushBack(v);
});
return callback(null, self.cache.popFront());
});
};
Scanner.prototype.next = function (numberOfRows, callback) {
if (typeof numberOfRows === 'function') {
callback = numberOfRows;
numberOfRows = null;
}
if (!numberOfRows) {
return this._next(callback);
}
var self = this;
var noMore = false;
var ret = [];
async.whilst(function() {
return ret.length < numberOfRows && !noMore;
}, function(callback) {
self._next(function(err, v) {
if (err) return callback(err);
if (!v) {
noMore = true;
} else {
ret.push(v);
}
callback();
});
}, function(err) {
return callback(err, ret);
});
};
Scanner.prototype.close = function (callback) {
var self = this;
this.server.closeScanner(this.id, function(err) {
if (!err) self.closed = true;
callback.apply(null, arguments);
});
};
module.exports = Scanner;